A 28-year-old woman with a history of recurrent oral ulcers and genital ulceration presents with acute vision loss and floaters. Fundus examination reveals retinal vasculitis with hemorrhages and cotton-wool spots. What is the most common site of uveitis involvement in Behçet's disease?

Explanation

## Most Common Site of Uveitis in Behçet's Disease **Key Point:** Posterior segment involvement (retinal vasculitis) is the most common and most sight-threatening manifestation of Behçet's disease, occurring in 70–90% of ocular cases. It is characterized by retinal hemorrhages, cotton-wool spots, branch retinal artery occlusions, and optic disc edema. ### Ocular Manifestations of Behçet's Disease | Site | Frequency | Clinical Features | Severity | | --- | --- | --- | --- | | **Posterior (Retinal vasculitis)** | 70–90% | Hemorrhages, cotton-wool spots, BRAO, optic neuritis | High (vision loss, neovascularization) | | Anterior (Iritis) | 40–70% | Hypopyon (pathognomonic), fibrin, keratic precipitates | Moderate (responsive to steroids) | | Intermediate (Pars planitis) | 5–10% | Vitritis, snowball opacities, epiretinal membrane | Low to moderate | | Ciliary body | Rare | Cyclitis, posterior synechiae | Variable | **High-Yield:** Behçet's disease is one of the few causes of **hypopyon uveitis** (anterior chamber pus level) — a sign of severe inflammation. However, posterior involvement is more common overall and carries greater risk of blindness. ### Pathophysiology of Retinal Vasculitis in Behçet's 1. **Vasculitis** of retinal arteries and veins (both branches affected) 2. **Endothelial infiltration** by lymphocytes and macrophages 3. **Thrombosis** and occlusion → cotton-wool spots, hemorrhages, retinal whitening 4. **Neovascularization** → vitreous hemorrhage, tractional retinal detachment (late complication) 5. **Optic nerve involvement** → optic neuritis, optic atrophy ### Diagnostic Criteria (International Study Group) - **Recurrent oral ulcers** (mandatory) + 2 of: - Recurrent genital ulcers - Eye lesions (typically posterior uveitis) - Skin lesions (erythema nodosum, pseudofolliculitis) - Positive pathergy test **Clinical Pearl:** The presence of **hypopyon** (layered pus in anterior chamber) in a young patient with posterior uveitis and systemic symptoms is highly suggestive of Behçet's disease, especially in Mediterranean, Middle Eastern, or East Asian populations. **Mnemonic:** **BEHÇET** = **B**ranch retinal artery occlusion, **E**dema (optic disc), **H**ypopyon (anterior), **Ç**otton-wool spots, **E**xudates (retinal), **T**hrombosis (vascular) ### Management Principles - **Acute exacerbation:** High-dose systemic corticosteroids (oral prednisolone 1 mg/kg/day) - **Maintenance:** Immunosuppressants (azathioprine, mycophenolate mofetil, cyclosporine) - **Biologic agents:** TNF-α inhibitors (infliximab, adalimumab) for refractory cases - **Anticoagulation:** Consider in cases with retinal vein occlusion **Warning:** Posterior uveitis in Behçet's can lead to severe vision loss due to repeated vasculitic episodes, neovascularization, and vitreous hemorrhage. Early aggressive immunosuppression is essential to prevent blindness.